1. Field of the Invention
The present invention relates to a heating appliance such as a frying pan, a saucepan, a high-sided frying pan or a iron sole plate having an inside and/or outside surface with a basic coating consisting of a thermostable resin such as a fluorocarbon resin, for example polytetrafluoroethylene.
2. Description of Prior Developments
Cooking containers including means for indicating the temperature of the inside surface of the container are known in the art. Those means generally comprise a temperature sensor integrated into the bottom of the cooking container and connected by conductors to an electronic module including a screen for displaying the temperature measured by the sensor.
The above means constantly inform the user of the temperature of the cooking surface of the container. The user can therefore determine the precise moment at which the cooking surface has reached a temperature sufficient to xe2x80x9csearxe2x80x9d meat.
Displaying the temperature of the cooking surface of the container also warns the user that the appliance is hot and could burn someone.
However, the above prior art means have the drawbacks of being complicated and of giving rise to problems of electrical insulation, in particular with regard to washing-up water.
In other embodiments known in the art, the handle includes a temperature indicator near the cooking container proper and consisting of a chemical compound which can change colour at a particular temperature. However, the temperature of the above area does not correspond to the actual temperature of the cooking surface, and so the change of colour of the chemical compound does not really indicate the temperature of the cooking surface.
The object of the present invention is to propose a particularly simple way to warn the user that the surface of the appliance is hot or has reached a sufficient temperature to use it.
In a heating appliance in accordance with the invention a decoration made up of a thermostable resin resistant to temperatures up to at least 200xc2x0 C. and of a chemical substance which changes colour as a function of temperature is applied over the thermostable resin which resists temperatures up to at least 200xc2x0 C. and which coats the surface of the appliance, the decoration covering part of the basic coating and adhering thereto because of the preferably simultaneous but possibly successive curing of the resin constituting the basic coating and the resin constituting the decoration.
The thermostable resin resistant to temperatures up to at least 200xc2x0 C. is preferably a fluorocarbon resin or a mixture of exclusively fluorocarbon resins or of fluorocarbon resins mixed with other thermostable resins.
The decoration is preferably based on polytetrafluoroethylene (PTFE).
The decoration is preferably applied by screenprinting or by printing by tampoprinting.
The decoration can be applied by the process described in French patent 2 576 253.
The above substance can be iron oxide used alone or mixed with other pigments or colouring agents, such as perylene red bonded to a black pigment.
Because the layer of thermostable resin in which the chemical substance is embedded is transparent the colour change can be seen through it.
If the basic coating is a fluorocarbon resin such as PTFE and the decoration is also based on fluorocarbon resin, curing the basic coating and the decoration enables the particles of the resin of the basic coating to be sintered with the particles of resin of the decoration, and when the curing is simultaneous, simultaneous sintering occurs, then ensuring excellent bonding of the decoration to the basic coating.
The change of colour of the chemical compound indicates to the user that the appliance is hot and therefore may burn someone and that the surface of the appliance has reached the correct temperature for its use.
The basic coating and the decoration are preferably covered with a continuous layer of transparent fluorocarbon resin which is also cured simultaneously with the resin of the basic coating and that constituting the decoration, enabling conjoint sintering of all the particles. The surface obtained then has optimum non-stick properties which are not affected by the presence of the decoration.
Other features and advantages of the invention will become more apparent in the course of the following description.